1. Field of the Invention
This invention relates to a method and apparatus for the treatment of infections, particularly abscesses such as cavernous tuberculosis, post-surgical intra-abdominal tissue conditions such as ulcers, vitiligo and psoriasis. More specifically, this invention relates to a system which allows the simultaneous drainage of an infected space and irradiation of an infected locus with laser-generated ultraviolet light. Additionally, this invention relates to a system which allows the simultaneous drainage of an endo-cavital space and irradiation of an infected locus with laser generated ultraviolet light.
2. Related Art
The use of ultraviolet light is a known and proven technique in procedures for sterilising liquids and for rendering drinking water safe for public consumption. For these purposes, short wavelength, spectrally non-selective ultraviolet light is used having a wavelength of from about 200 nm to about 350 nm. Within the so-called UV-C wave length range (200-270 nm), ultraviolet light is most effective in destroying the microorganisms commonly found in untreated water. Typical procedures are described by Dunn et al. in U.S. Pat. No. 5,900,211; by Nesathurai in U.S. Pat. No. 4,983,307; and by Wang et al. in U.S. Pat. No. 5,236,595.
It is generally accepted that microorganisms can be broadly grouped into five basic families; these are bacteria, viruses, fungi, protozoa and algae. These five families have different properties, occur in different habitats and respond differently to microbiocides such as antibiotics. Bacteria, fungi, protozoa and algae are generally characterised as comprising a cell wall, a cytoplasmic membrane and genetic material which is essentially DNA material. Viruses are somewhat different and generally have an outer coating of proteins surrounding genetic material which again is DNA material. When harsh ultraviolet light penetrates the microorganism, it causes disruption of chemical bonds within the DNA system thus preventing the DNA replication step required for reproduction of the microorganism. If a microorganism cannot reproduce itself, it is effectively dead.
However, the cells of different microorganisms are not the same: different microorganisms have different sensitivities to different wavelengths of light within the UV range; also the dose of UV light required to effect microorganism destruction varies for different microorganisms. The dose (or accumulated energy) is a product of the time for which the microorganism is exposed to the radiation, and the radiation power; most commonly, power is measured in Watts (W), and time is measured in seconds. This approach also appears to be applicable to vitiligo and psoriasis infections, even though microorganisms are not involved. Indeed for both of these infections the etiology is poorly understood and the causative agents for these infections have not been identified.
TABLE 1Average lethal dose densities fordifferent microorganisms (in mWsec/cm2) measuredunder a non-selective UV irradiation (a Xenon lampwith a UV band filter centered at 254 nm).MicroorganismDose/cm2MicroorganismDose/cm2Bacillus anthracis8.8Dysentery bacilli4.2Shigella dysentariae4.3Escherichia coli7.0Shigella flexneri3.4Streptococcus10.0faecalisCorynbacterium6.5Staphylococcus5.8diphtheriaeepidermisVibri commo6.5Bacteriophage6.5(cholera)(E. coli)Hepatitis8.0Salmonella10.0Influenza6.6Baker's yeast8.8Legionella3.8Mycobacterium10.0pneumophiliatuberculosisSalmonella paratyphi6.1Polio virus7.0Salmonella typhosa7.0
Table 1 shows that for different microorganisms, the measured lethal dose (in vitro) is not constant.
In addition to using UV light to sterilise fluids such as drinking water, lasers generating spectrally narrow-line light in ranges other than in the UV range have also had some use in medical therapy. In this context, it is relevant to distinguish between the use of non-UV lasers for surgical and other techniques and the use of UV light to treat microorganism infections. For example, in some therapeutic procedures, He—Ne or Nd-YAG lasers are used as localised heat sources, which stimulate blood supply and heat or destroy selected tissues; these laser radiation wavelengths are generally in the red or near infrared ranges. Any microorganisms present will only be affected by the laser irradiation if the heat generated by the laser causes the temperature of the microorganism to reach or exceed about 40° C. Although temperatures in this range are lethal to many microorganisms, the use of such lasers as a therapeutic tool to control microorganisms is circumscribed by the unacceptable damage this level of temperature can cause to surrounding uninfected tissues.
The treatment of destructive forms of endo-cavital infections, such as tuberculosis and post-surgical intra-abdominal abscesses, is a particularly difficult therapeutic area. The pathologically changed structures of cavital walls and substantial amounts of pus inside cavities prevent efficient administration of antibiotics. Also, many pathogens causing endo-cavital infections have become antibiotic-resistant. Similar considerations apply to the treatment of abnormal surface tissue lesions, such as abcesses, ulcers, vitiligo and psoriasis.
The procedures used at present to deal with endo-cavital infections are not as effective as is desired; a two step therapy is generally used. First, the cavity is drained to remove as much material as possible; this will include both cell debris due to the infection and to some extent the microorganisms causing the infection. Second, an antibiotic medication is administered to the patient. If the antibiotic(s) are to be successful, maximal cavity drainage is essential. In order to achieve maximal drainage, a hollow catheter is inserted cutaneously into the cavity either blindly or with guidance. Guidance is normally effected either by the use of an ultrasonic probe, or by the use of an endoscopic fiber-optic device included in the drainage catheter. But drainage is hampered by the flow characteristics of the fluid and pus containing cell debris being removed from the cavity, and by the relatively small size of the catheter in comparison with the potential volume of the cavity requiring drainage. An additional problem is the unavoidable presence of microorganisms both elsewhere in the cavity and on and around the catheter. As a consequence of these difficulties, in practice it is rarely possible to drain a cavity to the desirable level. It is also of importance that there is a real risk that some of the microorganisms are the so-called “super bugs”, which are mutant strains of common microorganisms such as staphylococcus; these strains are resistant to the currently available antibiotics.
Endo-cavital infection-caused diseases, such as destructive forms of tuberculosis and post-surgical intra-abdominal abscesses, present a rapidly growing concern internationally. In North America, post-surgical intra-abdominal abscesses are a major post-operative problem for a wide range of invasive surgical procedures. It has been estimated that the percentage of patients who develop post-surgical intra-abdominal abscesses ranges from about 30% for colorectal surgery, through about 15% for pancreatic or biliary surgery to about 2% for gynecologic surgery. Patients undergoing intra-abdominal surgery in North America alone, on an annual basis, number in the millions. These infections can be traced to several causes, including both airborne microorganisms and spontaneous leaks or perforations of either the biliary tract or the intestines. In other words, any procedure devised to treat such infections has to accommodate the fact that the infection will almost certainly involve several strains of microorganisms; each strain will respond differently to any applied procedure. Again, many of these considerations apply to abnormal surface tissue conditions.
It has been reported by Apollonov et al. in RU 2141859 (issued in 1998) that laser-generated ultraviolet light can be used in treating tuberculosis. By using a suitable fiber-optic catheter, the laser-generated UV light is used to irradiate and to destroy, within the lung cavern, the microorganisms, which are the cause of the tubercular infection. The method includes puncturing or draining the destructive cavern in the lungs, evacuating the purulent contents of the cavern and then exposing the interior surface of the cavern to ultraviolet laser radiation. This involves 10 to 12 minutes of exposure to the defocussed pulsed radiation of a solid-state laser at a wavelength from about 220 nm to about 290 nm, and energy density of 200 mWsec/cm2 with the pulse repetition frequency controlled as a function of the degree of destruction in the lungs, to ensure irradiation with an average energy density of 10 to 15 mWsec/cm2. A treatment session is concluded with a single introduction of 1.0 units of streptomycin or canamycin into the cavern. A course of treatment comprises 10-12 sessions of laser irradiation of the cavern.
However, there are several difficulties with the apparatus and the procedure described by Apollonov et al. These are as follows.    (1) The need for repeated puncturing of the cavern, which increases the degree of trauma experienced by the patient.    (2) Before the procedure is carried out, each repeated puncturing requires repeated radiological investigations, which increase the X-ray dose to which the patient is subjected.    (3) Each treatment session is concluded with a single introduction into the cavern of a full daily dose of an anti-tubercular medication dissolved in 2 to 3 ml of a 0.5% Sol. Novocain. The introduction of a full daily dose of anti-tubercular medication in a single dosage unit does not permit maintaining its bactericidal concentration within the cavern at a steady level throughout a period of 24 hours. In addition, because of the quantity involved, an introduction of such an amount of anti-tubercular medication at once frequently causes irritation of the mucous tissue of the bronchi draining the cavern, and this leads to a debilitating cough and expectoration in the sputum of a considerable quantity of the anti-tubercular medication that was introduced into the cavern; it also reduces the concentration of medication and lowers its bactericidal effect.    (4) To irradiate the cavern, Appolonov et al. used the emission of an available laser generating within the UV-C spectral range (266 nm, the fourth harmonic of the Nd:YAG laser). While that wavelength is still capable of producing bactericidal effect on tuberculosis pathogens, it is apparently not optimal for destroying the majority of tuberculosis microorganisms. This relationship is shown graphically in FIG. 1. Inspection of FIG. 1 shows that the most efficient wavelength to kill tuberculosis bacteria is about 250 nm, and that some UV wavelengths may not be efficient at all to treat tuberculosis. At the same time, other bacteria are more susceptible to the wavelengths efficient in the tuberculosis treatments. The use of a UV light wavelength which is not the most efficient wavelength, while it has specific values characteristic of each microorganism strain, or class of strains, means increased exposures, higher irradiation energy density and an increased risk of side effects.
Usually, patients to receive antibacterial treatment are already under a major stress, often with depressed immune systems after having undergone a major invasive surgical procedure, or suffering from a severe infection such as tuberculosis or intra-abdominal abscess. Thus, it is very desirable that any treatment procedure to deal with such infections would expose the patient to as little further stress as possible. It is therefore a prime concern to avoid having to surgically re-enter the cavity. The traumatic levels associated with repeated cavity re-entry implies that the level of antibiotics required to control the so-called “super bugs” may be more than the weakened patient can tolerate. Yet again, similar considerations often apply to abnormal surface tissue conditions such as ulcers and abscesses.